Suspension of magnesium hydroxide and materials and process for making same



. Patented Aug. 1, 1,939

aiss'aza MAGNES SPENSION 0F a seam some 1| MATERIALS AND'PROOESS FOR Roger A MacArthur, Wyoming, Ohio, assignor to The Philip Carey Manufacturing Company, a

corporation of Ohio No Drawing. Application December 28, 1936,

Serial No. 117,889

28 Claims. (Ci. ass-a2 This invention relates to the suspension ofv magnesium hydroxide in water and to suspensions or milks thereof, and is a continuation in part of my application Serial No. 646,299, filed Dec. 8, 1932, for Suspensions of magnesium hydroxide and materials and process for making same. This invention relates particularly to improving the consistency and suspension (nonsettling) properties of milks of magnesia, to improving the rate of solution of milks of magnesia.

in dilute acid, to improving the uniformity of structure and particle size of the magnesium hydroxide particles in milks of magnesia, and to improving upon the process of manufacturing milks of magnesia.

'Suspensions of magnesium hydroxide in water will be referred to herein as milks of magnesia.

flan; of magnesia containing about 8% of Mg(OH)a by weight is a widely sold and popular pharmaceutical preparation. Itis prescribed under the 'name Magma Magnesia by the U. S.

Pharmacopoeia X, which states that the solid content shall not be less than 7% by weight. It is generally used as an antacid and mild laxative for internal human consumption. In order that the'magnesium hydroxide in milk of magnesia made for pharmaceutical purposes be as chemically active as possible, it is desirable that the magnesium hydroxide be dispersed in water as completely as possible and in as finely divided a state as possible. This invention improves upon milks of magnesia, including the pharmaceutical.

preparations above described, and the manufacturing process thereof.

Milk of magnesia has heretofore been manufac-.

tured commercially for the most part according to either of two methods. According to one meth- 0d, milk of magnesia is made by treating a magnesium salt, such as magnesium sulphate, chloride, or basiccarbonate, with an alkali. The reaction is believed to be as follows; using W804 and NaQH by way 'of illustration:

When milk of magnesia is manufactured according to the above metathesis of a soluble magnesium salt and an alkali, the magnesium sul phate, for examplais made up into a solutiona It is necessary to remove. the contaminating substances. This is usually accomplished by allowing the gelatinous precipitatev of magnesium hydroxide to settle and decanting the supernatant liquid and/or by filtering. Further purification of the product is necessary and may be accomplished by adding distilled water to the separated magnesium hydroxide sludge and. again removing the wash water. The washing is repeated until the soluble salt content is so far reduced that it does not direct the taste of the washed magnesiumhydroxide and is not injurious to the human stomach. The concentration of Mg(QH)z is then adjusted until it is about 8% by weight. This method of preparing milk of magnesia is relatively costly and is also disadvantageous for the reason that it is extremely diflicult to reduce the soluble salt content sufficiently to meet the {requirements of the U. S.

Pharmacopoeia. Notonly is the method disadvantageous, but, also, the product that is made by the method is unsatisfactory for the reason The magnesia .used in the latter method is gen erally obtained from basic carbonate of magnesia which is the cheapest available source at the present time for making pure magnesium oxide.

Basic magnesium carbonate is believed to have the approximate formula 3MgCOaMg(OH) 2.311320 and calcihation it loses water and carbon dioxide and; is converted into substantially pure 45 magnesium oxide. The calcination is done in any suitable wayas by subjecting it to heat in a continuous kiln for a definite period of time. As

thus produced, the calcination is carried on until the magnesium oxide usually. contains only about u 5% to 8% of unchanged basic carbonate of magnesia. i

' The magnesium oxide produced as aforesaid.

or otherwise, may be converted into milk of I magnesia of about 8% concentration, for ex- I above.

ample, merely by mixing about Ave and onehali parts of the, magnesium oxide with about one hundred parts of water, either cold or hot. The hydration takes considerable time, and at first, a mass of sediment forms in the bottom' of the mixture with a cloudy layer or water there- The sediment consists of unreacted .or partially reacted magnesium oxide. lithe mixture is agitated from time to time for .several weeks, the sediment will largelydisappear and the material upon standing will form a lower layer of milk of magnesia in which the hydration of the magnesium oxide is substantially complete. The resulting milk of magnwa tends to settle leaving a relatively large layer of water,

i. e., about 40%. If hot-water is used the hydration oi the magnesium oxide is somewhat more rapid than if cold water had been used, but the settling of the milk 0! magnesia is greater at the end 0! the process. It the suspension 01 magnesium oxide is permitted to'stand untilthe hydration oi the magnesium oxide, using either hot or cold water, is substantially complete, and is then passed through a colloid mill, the milk of magnesia can be made of a somewhat more thick and creamyconsistency, and the tendency oi the milk 01' magnesia to settle can be somewhat reduced. Hydration of magnesium oxide and subsequent treatment 01 the hydrated material in a colloid mill is the method which is most generally practiced at the present thne in making milk oi magnesia. However, even the best milks of magnesia made accol'dim to this method tend to settle out upon standing as much as 10% to 30%.

It is an advantage and feature of this invention that milk of magnesia is atl'orded which is of a superior, creamy. consistency, and which has very slight tendency to settle. It is'a, further advantage and feature o! milk of magnesia made ac: cording to and embodying this inventim, that it has greater chemical activity than milks of magnesia heretofore made as determined by the ,rate of solution 0! the milk 01 magnesia in dilute acid. Further features and advantages of this invention relate to improvements-in the uniformity of structure and size of the magnesium hydroxide particles held in suspension'and to improvements in the method of making milk of magnesia. I v

- It is a further feature and advantage of this invention that milks oi magnesia having improved also by adding materials thereto which at, the

same time ailect thetherapeutic value of the milk of magnesia, while alsoimproving the. consistency, smoothness and non-settling properties of the milk.

When magnesium hydroxide-is made by the hydration of magnedum oxide, the degree and rate 01 hydration are dependent to some t upon the temperature at which the magnesium oxide has been calcined. Thus, when magnesium oxidehasbeen calcinedataboutm' 1,101, ex.-

ample, its reaction with water is very slow and does not yield a hydroxide which can be advantageously used as. milk of magnesia. It the temperature used in calcining is lower, for example, in the neighborhood oi 1400v 5 I"; the resulting magnesium oxide will become hydrated more rapidly and will produce a better milk of magnesia. Magnesium oxide burned at a temperature of about 900 1'. to 1100 1''. gives further improved rmllts. However, notwith- 10 standing the improvement eflected by burning magnesium oxide at lower temperatures, I have foundthat the hydrated oxide stillis'objectionable due to the excessive settling of the resultant product. Thus,'when basic carbonate 0! magnesia 15 isburnedat14001".andiscompletelyhydrated under the most iavorable conditions and sub- 4 jected to treatment in a colloid mill, the raultant product settles as much as 10% to 25% of the total volume. a e I have 'found that certain substances when added to milk of magnesia act as hydrating agents and so increase the hydration oi the magnesia that the resultant milkis of a smooth, creamy, thickened nature, and does not settle except to a a very slight degree. While this invention is not tobelimitedbythecorrectnessoianytheory which I may advance as to the phenomena that occur during hydration, I believe that thesubstances whichlusemaketheparticlesotmagnesium hydroxide in suspension more hydrous, and that by virtue of alteration intheir size or or increase in the adhesion of water thereto, orv both, the magnesium hydroxide particles become more hydrous and'occupy more extent in space.

The result, in any event, is that the milk-of magnesia is given a creamy consistency and settles very little to hydratlm of the magnesia.

lnthepracticeotthisinventionthehydrw-gtion of a suspension oi magnesium hydroxide particles in water is increased by including in the suspension an electrolyte which is adsorbedby the magnesium hydroxide particles and whichis itself adsorpti've ofwater. Thus the conglomer- 5 ates 0! magnesium hydroxide particles, adsorbed elelectrolyte, and bound water, occupy a greater extent in space and bind increasedamounts of water thereto thus electing more .complete hydration. v 3

When magnesium oxide is mixed with water, either hot or cold, it combines chemically with l the water and is gradually converted into magnesium hydroxide. The physical state of the resulting magnesium hydroxide will depend upon 55 the degree of hydration thereof. Thus the term "hydration" covers not only the conversion of MgO to Mg(OI-I)z, but also the association 01' water with the Mg(OH): particles. The electrolytic hydrating agents for magnesium hydroxm ide which are employed according to this invention promote the association -oi water,with magnesium hydroxide particles and afiord substantially greater hydration than occurs in the case of a suspension or magnesium hydroxide particles as I similarly prepared but .in the absence of an electrolyte, for example, when the suspensim is) formed by hydrating magnesium oxide in pure water in the usual way. Electrolytic hydrating agents according to this'linvention promote the n) formation or suspensions oi magnaium hydroxide which have creamy and substantially non-settling characteristics. The electrolytic hydrating agents used in the practice of this invent n are believed to street suspensions of mag- 7s trolytic hydrating agent will be understood to cover the methods and substances respectively herein described.

This invention may be described for the purpose of illustration in connection with the use of magnesium bicarbonate as an electrolytic hydrating agent. If a milk of magnesia is made from magnesium oxide which has been burned at 1400 F. in the. proportion of about five and onehalf parts of oxide to one-hundred parts of water and the mixture of oxide and water is permitted to stand while cool for about twelve to twentyfour hours, the bulk of the magnesium oxide will be hydrated with the formation of a suspension containing about 8% of magnesium hydroxide.

However, I have found that the hydration of the magnesium hydroxide is greatly increased by adding thereto about one-half percent to one and onehalf percent of magnesium bicarbonate on the weight of dry MgO'. The magnesium bicarbonate may be added in the form of a solution. Immediately after the magnesium bicarbonate solution is added, the suspension of magnesium hydroxide becomes thicker and creamier and its non-settling properties are greatly improved. Notwithstanding its thickened creamy consistency the milk of magnesia has highly desirable pouring characteristics. The color'of the milk of magnesia is unchanged. The presence of the magnesium bicarbonate does not aifect the taste of the milk of magnesia; Moreover, the physiochemical Characteristics of the milk of magnesia are not changed.

I have found that where electrolytic hydrating agents are used there is an optimum amount which produces the greatest degree of hydration. Thus, for example, in the case of-magnesium oxide which hasbeen burned at 1400 F. andhas been hydrated with cold water for twenty-four hours to form an 8% milk of magnsia'I have found that the percentage settling of the resultant mix gradually decreases upon the .addition of magnesium bicarbonate thereto up to the point where about one percent of magnesium bicarbonate on the weight of magnesium oxide is added, and that upon adding inc ased amounts of magnesium bicarbonate above 'about one and one-half percent, the percentage settling begins to increase. Theamount of electrolytic hydrating agent that gives optimum results can readily be determined by trial of the agent in various amounts.

The optimum amount of stabilizer or'electrolytic hydrating agent varies to seine extent,, depending upon the temperature'at'which magnesium oxide has been burned. Thus, in the case of magnesium oxide which has been produced by calcining basic magnesium carbonate at about 1100? F. only one-tenthpercent of magnesium bicarbonate on the weight 'of magnesium oxide is necessary to give optimum results.

While there is an optimum amount or range ofelectrolytic hydrating agent at which the best results are secured, there is an efiective range of amounts of electrolytic hydrating agent within whichsubstantially improved consistency reactivity and non-settling properties are secured. These improved characteristics of magnesium hydroxide suspensions according to this invention, may readily, be determined by comparison with the characteristics of magnesium hydroxide suspensions made in substantially pure wateror without the presence of an electrolytic hydrating agent as mentioned herein.

Ordinarily, it is preferable not to add an excess of electrolytic hydrating agent beyond that which aifords optimum. results or is within the effective range for affording improved hydration as thereis danger of permanently affecting the magnesium hydroxide particles so that upon reducing the amount of agent to optimum or effective amounts full hydration of the magnesium hydroxide particles cannot be achieved and an inferior product will resulti Likewise other substances may contaminate a suspension of magnesium hydroxide particles as they. adversely affect the capacity of the magnesium hydroxide particles to become. highly hydrated and may permanently affect the capacity of the magnesium hydroxide particles to become highly hydrated even though the contaminating substances are removed. It is normally preferable in the practice of this invention to hydrate magnesium oxide insubstantially pure water, an electrolytic hydrating agent being incorporated in the magnesium hydroxide thus formed in not more than lytic hydrating agents such as magnesium bicarbonate produce ions which become adsorbed upon the particles of magnesium hydroxide. Thus, in the case of magnesium bicarbonate, the formula of which is believed to be Mg(HCO:)2, it is be:

lieved that ions thereof become adsorbed upon the magnesium hydroxide particles. While it cannotbe determined which ion is responsible for the efiects produced, it is believed that the HCOF ion is chiefly active in this regard and becomes adsorbed by or associated with the magnesium hydroxide particles. The ions adsorbed by the magnesium hydroxide particles are themselves adsorptive of water and thus it is believed that the suspension becomes more than a mix-.

ture of magnesium hydroxide particles in water 5 and consists of numerous separate entities consisting of magnesium hydroxide particles. plus adsorbed ions plus bound water. These entities tend to make the mass creamier and thicker and tend to reduce the rate of settling; However, different amounts of electrolytic hydrating agent the conglomerates. At a certain point the size of the conglomerates is believed to reach a state 'whereat maximum colloidal effects are produced;

Thus, it is that the addition of very small are believed to exert different ultimate effects on the particles as by controlling the size of amounts. of electrolytic hydrating agent such as may thereafter so further aflect the size of the particle conglomerates thatthemilkof magnesia is again thinned and given increased settling tendencies.

Whilethisinventionhasheen illustrated hereinaboveinconnectionwiththeuseoium .bicarbonateasanelectrolytichydrating agent,

numerous other electrolytic hydrating agents mayalso be used. Thus,in generaL aci'ds, bases and'saltshavesomeeil'ectontheultimatehy dratimotumhydroxideandtheiol lowing'specidc examples oi electrolytic-hydrat- 'ingagentshavebeeni'oundtomcreasethethickness and resistance to settling of milk oi magnesia, i. e., the salts sodiumammoniuin ierrocyanide, sodium carbonate, sodium acetate, ammonium acid phosphate, magnesium sulphate,

sodium oxalate,'sodium bitartrate, m sodium bisulphite, magnesium citrate, magnesium carbonate yd at um the bases ammonium hydroxide, sodium hydrotide and potassium hydroxide; and the acids phosphoric acid, sulphuric acid, carbonic acid, citric aeidandtartaridacid. Itisbelieved'thatthe' hydrating'agents whichmaybeused-inthepractlce at this invention are electrolytic. asv nonelectrolytesorsubstantiallynon-electrolytessuch assilicic acid, sugar, oleic acid, and alcohol, give no appreciable eil'ect in the thickness orresistancetosettling'of :1.- w hydroxide The optimum amount 01' electrolytic hydrating agentthatisuseddependsinpartuponthesubvstance-thatisuiiedasahydmtziriga'g uit. For

example,inthe caseof48% milkot madeirommagnesimnoxidecalcinedfrombasic :-H n carbonate at 1400" l '.,whichhasbeen aged twenty-four hours, the following amounts ot electrolytic hydrating agcnt'based on the dry' weightoithemagnesiumoaideusedwereiound to give substantially optimum results:

' Per cent 1 to 2 1 1 to 2 s to s Salts 8:01.; 10 to 20 Mg804 1 to 2 (NHlJiH-PO! -Japproximately) 2 H8(HCO:): .55 to 1% K800333110", ")5 to 1% since the percentages given in the foregoing table are based on the dry weight otmagnesium oxide, the percentages of the diiierent electrolytes'are somewhat less than the figures above given when based on the dry weight oi'the mag- .ncsiu'm hydroxide in the resulting suspension. The ?0% given in the above table in connection with hydrochloric acid and sodium chloride is as large an amount of electrolyte as itis preferable to employ in the practice of this invention;

with an electrolyte such as magnesium bicarbon-' ate much lus of electrolyte is preferable. Moreover, it is preterable that there be less than 20% 0!. dissolved and undissolved substances in the arlpaision other than um hydroxide dttheelcctrolytesthe vastmadorityaresuiiiciently'solublesothattheycanbepresentin aufldent amount tobe eii'cctive as hydraflng a-Jta. Howeventhereareaveryiewsuhstances aushashydratedllmathioflh, which aretoo irlolulleinwater to-be elective ashydrating a itafla' hydroxide particles. In

thecase oihydrated limeits low degree oi solubility combined with the fact that the OH- ion is relatively weak in its hydrating eiiect on magnesium hydroxide particles in suspension, prevents suiiicient OH- ion concentration being builtuptoresultlnhydrationctthemagnesium hydroxide particles and such .OH- ions that areliberatcdinsteadottendlng-tomakemilkoi Intheselectioholaneleotrolytichydrating a nt for use in the practice of this invention it is preferable toselect onewhich isbromatologi- .cally unobicctionahle, that is, one which is compatible with the-introduction thereof into the humanstmnachwhcnusedinamountssuiiicient to improve the consistency and nonsettling mialitiesotmilkoimagnesia. Inthisconnection acidsareharmlesstromthepointoiviewotthe positive acid'radicalashighconcentrationofa positiveacidradioalisimposalbleinasuspenaion of hydroxide. With regardto the negativeradinlsotacidsitisbelievedthatradi- 'cals existing, for example. as the ions Ch BO4=,

P04 HPOF HsPOr, borate, CO;=, HCOr, tartratr, acldtartrate-g and citrate: are bromatologicallyacoeptable. Theuseoicertainbases,

\ is generally undesirable where tmixtureistobetakenintcmally.

the resul as 03- concentration is in general tome and also gives an undesirable taste to the .In connection with the me of salts, positive ions such as NR4", Kt Na+, Cafi, Mg++, and Fe" or 1=e+++. arevin general bromatologically harmless by and when combined with negatNe ions such as those mentioned above in connection with acids i. e., (31-. GOP, P04 HPO-F, HzPOp boratr. C0:=, HCOr, tartrate, acid .tartrate-, citrate-, and acetateform salts which are bromatologically acceptable.

Electrolytic hydrating agents which are especiallydesirablebothiromthepoint' oi view ct being bromatologically un'obiectionabie and from the point 0! view of having requisite solubility and higheilectivenes to accomplish increased hydration of magnesium hydroxide particles'inand acid'tartratr. the alkali-metal salts of the above acids, the alkali-metal chlorides, nitrates tea, the sulphates, acidphosphates, acid and acid tartrates of calcium. magand iromand the normal-carbonates ot um hydroxv eluding acids, bases, and salts, which are effective electrolytic hydrating agents and a number of those which meet bromatological requirements, the majority of them afiect the taste of the milk of magnesia with which the substances are mixed and in some instances the therapeutic properties of the milk are also modified, and while this may be advantageous in certain instances it is not desirable where a pharmaceutical preparation, answering standard specifications, is desired. In this connection it is preferable to employ as electrolytic hydrating agents according to this invention substances such as the carbonates of magnesia, e. g., Mg(HCO3)2, MgCO3.3H2O, and/or HzCOa, as these substances add no noticeable taste to milk of magnesia and add nothing to milk of magnesia which is not already there in some form, namely,-MgO, CO2, and H20. Moreover, the substances named give very satisfactory results even when used in -very small amounts such as one-half percent to one and one-half percent on the weight of magnesium oxide due to the efiectiveness of the bicarbonate ion which they yield in water solution as a hydrating agent.

In some instances it may be desirable to add electrolytic hydrating agents which not only improve the consistency and non-settling properties of milk of magnesia but also modify and improve its therapeutic properties. Thus, substances such as magnesium sulphate, sodium citrate, disodium phosphate, or salt may be used 1 as hydrating agents. These substances are saline laxatives and give the resultant milk nesia increased laxative effect.

,The electrolytic hydrating agent may be in corporated with and included in the milk of magnesia in a variety of different ways. Heretofore, it has been stated that in the case of'magnesium oxide calcined from basic carbonate ofimagnesia at 1400 F., it is preferable to add at least part of the electrolytic hydrating agent after the magnesium oxide has been treated with water for twelve to twenty-four hours in the case of cold water. If hot water is us'ed' in hydrating the magnesium oxide the result is somewhat inferior to the results which are obtained when cold water is used, namely, the settling may be about 2% instead of 1% of the volume of the resulting mixture.

The electrolytic hydrating agent can be added to the magnesium oxide-prior to the treatment of the magnesium oxide with water or at sub-, stantially the sametime that the magnesium of mag- -oxide is treated with water. In such case, however, the results are not as satisfactory in the case of magnesium oxide which has been calcined at 1400 F. and the resultant product where optimum amounts of electrolytic hydrating agents are used shows-a final settling of about 3% to 7%. In the case of magnesium oxide calcined at lower temperatures such as 1100 F. excellent j products can be obtained where the electrolytic hydrating agent is present at the time that the magnesium oxide is first treated with water. Thus a milk of excellent consistency and nonsettling properties can be obtained by adding about 1% of Mg(HCO3)2or IV;% of MgCO3.3HzO to the oxide prior to the hydration thereof with water.

When the electrolytic hydrating agent is added-- to the magnesium oxide prior to or substantially simultaneously with the treatment of the oxide ions.

tially no sediment occurs. If more than the optimum amount of electrolytic hydrating agent, e. g., 3% of magnesium bicarbonate is added prior to or substantially simultaneously with the treatment of the oxide with water, the result is most extraordinary as a solid pseudo-gel is formed. The gel is of a translucent character and is easily broken up to give a translucent. milk of 'magnesia which settles very little, i. e., about 1% to 2%. This product is very active toward dilute acid and is superior in this respect to milk of adsorbed CO2 with water. In the case of magnesium oxide calcined at very low temperature, such as 900 F. to 1100 F., suficient aeration can be obtained in a few minutes. In the case of magnesium oxide calcinedat higher temperatures, the aeration may require several hours. If

the aeration is continued too long, effects such as above described where more than-an optimum amount of oxide is added prior to treatment with water will result, namely, the milk of magnesia will tend to form a pseudo-gel. In such case, it

is believed that the carbon dioxide which is adsorbed upon magnesium oxide particles forms carbonic acid when the oxide is treated with water, the carbonic acid ionizing to form bicarbonate ions (HCOr) and positive hydrogen It is believed that ions are adsorbd upon the particles of magnesium hydroxide. The positive hydrogen ions are'believed to be neutralized by the OHr radical of the Mg( OH)z leaving HCOaions surrounding the particles of magnesium hydroxide and binding water thereto to create conditions favorable to colloidal gel conditions.

Whilecarbonic-acid can be used as an electrolytic hydrating agent in the practice of this invention, .it is ordinarily preferable to employ of CO2 have been adsorbed from the air by aerat- -ing magnesium oxide or when a proper amount magnesium oxide with water to form a substantially non-settling milk of magnesia according to this invention, it is of advantage that magnesium oxide admixed with a hydrating agent can be made up in advance and that a composition can be made up and sold containing magnesium oxide in combination with a'substance which modifies the hydratingcharacteristics thereof. Thus, for example, magnesium oxide burned from basic magnesium carbonate at temperatures ranging from about 900! F. to about 1800 F. may be made up as a product in combination with an electrowith water, the tendency of the oxide to forni a f ly tichydrating agent, e. g., magnesium carbonate sediment is greatly reduced and in the case of optimum amounts of hydrating agent substantrihydrate, the magnesium carbonate trihydrate being, for example, about to,1 ofthe the magnesium oxide, in presence of water and the electrolyte, to magnaium hydroxide. In this connection the amount of electrolytic hydrating agent will depend to a certain extent upon the particular hydrating agent used and upon the temperature at which the magnesium oxide has been burned. as hcreinabove explained. While it is preferable to mix magnesium oxide with an electrolytic hydrating agent which is-ina dry state, it is within the scope of this invention to 'mix the magnesium oxide'with a liquid hydrating agent. e. g., magnaium bicarbonatesolution.

The residue of unburned basic magnesium carbonate (about 5% to 8%) which isusuallypresent in magnesium oxide calcined from basic magnesium carbonate does not have an appreciable eifect as a hydrating agent. It is believed that the basic magnesium carbonate which has been subjected to the calcination has been modified so that it isincapable of forming ions which are adsorbed upon the particles of magnesium hydroxide with resultant increase in hydration. .More over, the traces of other impurities in-the calcined -mag nesium oxide also have no appreciable eifect.

and it is believed that such impurities actually make the resulting milk of magnesia of increased thinness and increased tendency to settle. However, by'incorporating an electrolytic hydrating agent with magnesium oxide before or after treat ingsamewithwatersothattheagentisinan' effective state to promote the hydration of the magnesium hydroxide and to ionise so that ions are adsorbed by the magnesium hydroxide particles and bind-water thereto, a milk of magnesia can be made which-is creamyin consistency and has little 'or no tendency to settle even after standing for, many months unagitated.

An illustration of one way by which milk of magnesia may be advantageously made in the practice of this invention, follows: 500 gallons of cold water (about to C.) are placed in a suitable tank equipped with a ,poweredstirrer. preferably of the high speed propeller'type. 250. pounds of magnesium oxide calcined at a tempe ature of about 900 F. to 1400 F. are then added to the water and the mixture is stirred until the suspension is substantially homogeneous. The suspension is allowed to stand over night. namely, about 12 hours- (or longer if more convenient) when it'is stirred again.- Intermediate stirring can be employed but is'not essential. During the subsequent stirring than is added to the suspension 2.5 pounds of memo-mam tal form or if more cmvsnient 18 gallons of 2% MgfliCQs): solution, which solution, of high purimmediately thickens and becomes of. a creamy consistency.

ity, is readily and cheaply a'vailable at plants which are engagedin the manufacture 'of basic carbonate of magnaia from Dolomite rock. The

I fitter stirring until the mixture is substantially homogeneous the is aromas I ready for bottling and shipment without further treatmt.

The resulting product has exceedingly good pouring properties and retains its desirable condition indeflmtely. Even after standing for periods suchas four months or more the suspensions will not, settle more than about 1% to 3% of the total volume. Thus the milk'of magnesia issubstantially non-settling.

Theresulting productis alsofound bytest to exhibit increased reactivity as evidenced by increased rate of solution of the suspended magnesium hydroxide particles in dilute cid. Moreover, the resulting product is than to be more completely and uniformly soluble as evidenced by the occurrence of diminshed insoluble or diiiicultacid. Both of these improved characteristics are of importance, particularly when the milk of magnesia is taken internally, as it is desirable to have the milk of magnesia dissolve in the stomach acid as quickly and completely as possible. The improved product embodying and manufactured according to this invention hasbeen tested in comparison with several prominent and widely advertised brands of milk of magnesia at present .ly soluble residues after treatment with dilute on the marketby the following test procedure: A

cleanbeaker is placed upon a black surface and 1 cc. of the sample ofmilk of magnesia (about 8% concentration)" is pipetted into the beaker. 200 cc. of distilled water is then added to the sample and after thorough stirring 100 cc. .of 0.03 normal hydrochloric acid is quickly poured into the beaker, at the same time starting a stop-watch. The end point of the test is taken as the time elapsed when no further perceptible change in clarity of the solution takes place. The

presence of any insoluble residue is noted, also the degree of clarity of:- the final solution. While the end point is not extremely precise, the differences found in treating diiferent brands of milk of magnesia are very marked, and dinerent tests of the same sample usually check within about 5%. The following is a comparative tabulation showing the reactivity range of various brands of milk of magnesia which were tested, the time of reaction being measured in seconds and the amount of insolubleor difiicultly soluble residue being noted. Withregard to the insoluble residue, a ruidual amount of 0.5 milligram per cc. of original milk-is regarded as a slight amount, 1.0

milligram per cc. of original is' regarded as a moderate amount, and 1.5 milligrams per cc. of

original is regarded as a large amount.

. f W Amounrmmsoluble Trace to slight.

Moderate. Moderate to large. Slight to moderate. t" Slig so to moderate. Moderate.

0 M rate to large.

Moderate.

nation.

on ved tembod a" "s? m B a os-2m ss-aao M Iii-1m I it is thus seen that the improved milk of magnesia embodying and made according to this invention exhibits greatly increased reactivity with dilute acids and contains a lessened amount of residue which is insoluble r difiicultly soluble in dilute acid. In performing the above tests it hydrating agents according to this invention, is

not necessarily the point at which there is greatest reactivity in dilute acid and that these advantages of the improved product do not necessarily run parallel to each other. Accordingly,

- the achievement of any of these improvements afiorded by the use of hydrating agents according to this invention is to be regarded as coming within the scope of this invention.

1 The improved product embodying this invention has been examined under the microscope and photomicrographs of the improved product have been compared with photomicrographs of several prominent brands of milk of magnesia now on the market. As a result of the comparison it has been found that the improved milk of magnesia of the present invention possesses greatly increased uniformity of structure and size of particles. Photomicro'graphs of the improved product showed fields wherein the magnesium hydroxide particles were remarkably uniform and contained substantially no large agglomerates. On the other hand, pho'tomlcrographs of other milks of magnesia were in striking contrast thereto and showed fields containing very wide ranges in structure and size of particles and containing many \crystals or masses of relatively large size. Whilefthis invention is not limited by the correctness of theories advanced herein, it is believed that the increased uniformity of particle structure and size is responsible at least in part for the improved non-settling and reactive properties of milk'of magnesia embodying and madeaccording to this invention, and it has been pointed out hereinabove that electrolytic hydrating agents employed according to this invention are believed to affect the size of magnesium hydroxide particles so that conditions of increased colloidality are achieved.

While tests have been given hereinabove of improved properties of milk of magnesia embodying and made according to this invention, it is to be understood that these tests have been given merely for the" purpose of illustrating improvements which may be afiorded according to this invention and that the advantages of this invention-can be achieved when there is considerable variation from optimum conditions as hereinabove set forth and that this invention is to' be limited only by the appended claims.

In the manufacture of. milk of magnesia, ac cordingto this invention, it is of advantage that expensive procedure in methods of making milk of magnesia heretofore practiced is avoided. Thus, the. long periods of hydration of MgO with intermittent agitation are avoided. Moreover, all necessity for colloid mill treatment in v homogenizing the milk is avoided. One is permitted to use the cheapest source of pure magnesia, namely, MgO' burned from basic carbonate of magnesia. Moreover, the expensive methods of metasynthesis of magnesium hydroxide with resulting washings, etc., is avoided.

alternate method of making milk of magnesia in the practice of this invention is to employ magnesium oxide which has been burned at low temperature such as 900 F. to 1100 F.

and which is very active. This material, due to its activity, can be readily stabilized by anelectrolytic hydrating agent formed in the water as a result of aerating the oxide or a suspension of the oxide so as to absorb CO2 and form carbonic acid. Thiscould be done, for example, by stirring a suspension of the oxide with a propeller stirrer or with compressed air or CO2 gas in a relatively short time.

. ,While this invention has been illustrated chiefly in connection with milk of magnesia made by hydrating magnesium oxide suspensions it may also be practiced in stabilizing suspensions of magnesium hydroxide made by metasynthesis of soluble magnesium salts and suitable bases. In such case an electrolytic hydrating agent should preferably be added after the suspension of magnesium hydroxide has been made and washed free of soluble salts as the hydrating agent would, to large extent, be removed during the washing operation. However, milk of magnesia made by metasynthesis as above described aiiords a milk of magnesiawhich is considerably less creamy and non-settling in character as compared with milk of magnesia .which is made by the hydration of magnesium oxide though the same hydrating agents are used.

While this invention has been described in con nection with certain examples,-it is to be understood that this has been done merelyior the purpose of illustrating the practice of this invention. By thus mentioning numerousspecific examples and giving general principles which are believed to be applicable, one skilled in the art will have no difiiculty in selecting an electrolytic .hydrating agent and effecting the stabilization of milk of magnesia according to this invention. It is an advantage of using electrolytic hydrating agents in the practice of this invention that they stabilize milk of magnesia by promoting.hydration thereof thus making'the resulting milk more active and of superior therapeutic value without theaddition of gelatinous or viscous organic substances which are undesirable. Moreover, by using the carbonates of magnesia including the normal, acid, and basic carbonates of magnesia or carbonic acid in the stabilization of milk of magnesia, no objectionable alteration in taste, color, appearance, or physiochemical content is made and atthe same time the consistency and chemical activity of the milk of magnesia are greatly improved, and the milk of magnesia is rendered substantially non-settling.

I claim:

1. A method of making milk of magnesia which comprises forming a suspension of magnesium hydroxide particles in water by hydration of magnesium oxide with water, there being incorporated with the suspension a dissolved electrolytic hydrating, agent in an amount efiective to produce substantially greater hydration of the magnesium hydroxide particles than occurs in a 3. A method of maldng of a'which' comprises forming a suspension of magnesium hydroxide particles in water, said suspension be- 5. Amethodofmakingmilkofmagnesiawhich comprises hydrating magnesium oxide in water by hydration reaction between said oxide and watertoiormasuspensionotthe magnesium hydroxidein water, said hydration reaction being carried out in the pruence of an amount of disi solved electrolytic hydrating agent eil'ective to impart substantially gerater non-settling property -1- tothe suspension than if saidsuspensionwere prepared but in the absence of saidgen - 6. Armethod of making milk oi. magnesia which comprises hydrating with substantially purewater magnesium oxide burned at a temperature of from about 900 1". to about 1800' 1". until the bulk or the magnesium oxide has been converted to magnesium hydroxide particles and forming a suspension of said magnesium hydroxide particles in said substantially pure water, and thereatter the non-settling property of the suspension or magnesium hydroxide particles and increasing the reactivity thereof to dilute acid by incorporating not more than about 20% of a dis- An solved electrolytic hydrating agent (on the weight of dry um oxide) in the suspension and in sumcient amount to eflect such increase.

7. A methodoi making milk of magnesia which comprises substantially simultaneously treating magnesium oxide burned at a temperature or from about 9M 1". to about 1100' P. with water tohydratesaid oxideto form a suspension of hydroxide particles in water and with w an amount oi. dissolved electrolytic hydrating 5 agent elective to impart substantially greater non-settling property to said 11 than if thesuspmsionwere'similarlypreparedbutin the absence oi said agent, ,the amount of electrolytic ydrafl l agent being not more than 20% on the weight of dry magnesium oxide.

s. A method of making milk of hav-' ing substantially greater reactivity to dilute hydrochloricacid than a milk of ofllke ooncentraflon subnantially tree or an electrolyte and P epared by hydrating umoxide in water, which comprises forming a suspension of am hydroxide in water containing in the I neighborhood of eight per cent. 0! magnesium hydroxide by hydrating oxide by reaction with water, a dissolved electrolytic hydraflng agent being included in said suspension f-in suiiicient amount to increaselthe reactivity o i."

thesuspensionto dilutehydrochlorlc acid aseompared to the reactivity to. dilute hydrochloric acid of a suspension oi like concentration similarly P epared but not containing said agent, thereby producingamilkof havingtheincreaaedreactivity aforesaid. ldmethod oimakingmilkoi'magnesiahav- 7g inggreaterreactiviiato-dilute hydrochloric acid than a milk of magnesia of the same concentration but consisting of magnesium hydroxide suspended in substantially pure water, which comprises forming a suspension of magnesium hydroxide in water by hydrating powdered magnesium oxide by reaction with water, the reactivity to dilute hydrochloric acid of the suspension-being increased substantially beyond the reactivity to dilute hydrochloric acid of a suspension 01 the same concentration but conslsting of magnesium hydroxide suspended in substantially pure water by the inclusion in the suspension of a dissolved electrolytic hydrating agent in an amount adapted to produce such increase, the resulting suspension beingiree of excess of said agent or of any other substance eflective to cause the reactivity of the suspen-- slon to dilute hydrochloric acid to be approximately the same as or less than the reactivity to dilute hydrochloric acid 01' a suspension consisting of magnesium hydroxide suspended in substantially pure water, thereby producing a milk of magnesia having the increased reactivity tov dilutehvdrochlorlc acid aforesaid.

10..A method of making milk 01 magnesia which comprises forming a suspension of magnesium hydroxide in water by hydrating magnesium oxide with water and thereafter increasing' the non-settling property of the suspension by incorporating a dissolved electrolytic hydrating agent therein in suillcient amount to aflect' such increase, said agent being selected from the group of electrolytes consisting of acids having the anions SO4=, H804, PO4 HPO4=, HzPOr. C0:=. HCOr, tartrate=, and acid tartrate, the

alkali-metal salts'oi the above acids, the alkalimetal chlorides; nitrates and borates, the sulphates, acid phosphates, acid carbonates and acid tartrates of calcium, magnesium and iron and the carbonates of magnesium.

ii. In the manufacture of milk oi magnesia wherein um oxide is hydrated in water to form a suspension 0! magnesium hydroxide particles in water, the steps comprising hydrating said magnesium oxide with waterto form magnesium hydroxide particles in the presence of a dissolved electrolytic hydrating agent in effective amount to produce a milk or magnesia having greater non-settling propertythan it the milk of magnesia were similarly hydrated but in the absence oi' said agent, said agent being selected from the group of electrolytes consisting of acids having the anions 804 HSOr, PO4 HPO4=, HnPOFQ CO':=,' HCOa, tartrate=, and

acid tartratr; the alkali'metal salts of the above acids, the alkali-metal chlorides, nitrates and boratea'the sulphates, acid phosphates, acid carbonates and acid tartrates of calcium, magneslum and iron and the normal carbonates of magnesium.

12. Asaproduct,milkot otacreamy and very slight-settling character comprising primarlly magnesium hydroxide particles in ous suspension, said milk of magnesia comprising water, urn hydroxide particles formed by interaction between magnesium oxide and and a dmolved electrolytic hydratlonagent which is eil'ective in the amount present in said product to give the milk of magnesia substantially greater non-settling property than a milk of magnesia similarly prepared but subflantlally tree of an 13. As a product,=milk of a of a creamy and very slight-settling charactercomprising pri- .marilymagneaium hydroxideparticlesin aqueof an electrolytaand said agent being selected from the group of electrolytes consisting of acids havingthe anions SO4=, HSOF, PO4 .iHPO4=, HEOF, COa=, HCOr, tartrate=, and acid tartrate-, the alkali-metal salts of'the above acids, the alkali-metal chlorides, nitrates and borates, the sulphates, acid phosphates, acid carbonates and acid tartrates of calcium, magnesium and iron and the normal carbonates of magnesium.

l4. As a product, milk of magnesia of a creamy and very slight-settling character consisting essentially of magnesium hydroxide particles formed by hydrating magnesium oxide powder with water, the concentration of the suspension being in the neighborhood of eight per cent., and a dissolved electrolytic hydrating agent in an amount which is efifective to give the milk of magnesia substantially greater non-settling property than a milk at magnesia of like composition but substantially free of an electrolyte.

15. As a product, milk of magnesia of a creamy and very slight-settling character consisting essentially of water, magnesium hydroxide particles in suspension in said water, said magnesium hydroxide particles being formed by interaction of magnesium oxide with water, and an electrolytic hydrating agent which is present in an amount adapted to impart to the suspensiong'reater reactivity to dilute hydrochloric acid than that of a suspension of like concentration of similarly .formed magnesium hydroxide particles in substantially pure water, said agent being selected from the group of electrolytes consisting of acids having the anions SOi=,VHSO4-, PO4 HPO4=, HzPOr, COa=, H0033 tartrate=, and acid tartrate-, the alkali-metal salts of the above acids, the alkali-metal chlorides, nitrates and borates, the sulphates, acid phosphates, acid carbonates and acid tartrates of calcium, magnesium and iron and the normal carbonates of magnesium.

16. As a product, milk of magnesia of a creamy and very slight-settling character consisting essentially of a suspension of magnesium-hydroxide particles stabilized by a saline laxative which is an electrolytic hydrating agent in said milk of magnesia, said saline electrolytic hydrating agent having laxative properties being effective to increase the non-settling property of the magnesium hydroxide particles in suspension in comparison with a suspension similarly prepared but in the absence of said agent, and said magnesium hydroxide particles having been formed primarily by' interaction between magnesium oxide and water. a

17; As a product, milk of magnesia of a creamyand very slight-settling character consisting. es-

sentially of a suspension of magnesium hydroxide particles in water and stabilized by an electrolyte in efiective amount to increase the non-settling property of the magnesium hydroxide particles in suspension,- said electrolyte consisting essena quantity employed. 7

18. As .a' product, the composition comprising tially of one yielding bicarbonate ions in solution and being bromatologlcally acceptable in the magnesium oxide produced by calcining basic magnesium carbonate at a temperature of from about 990111. to about 1800 F said magnesium oxide thus produced being in admixture with a small proportion of magnesium carbonate trihydrate.

19. As a product, the composition comprising magnesium oxide produced by calcining basic magnesium carbonate at a temperature of from about'900 F. to about 1800 F.,.said magnesium oxide in major proportion in said product being in dry admixture with a substance which is f adapted to become an electrolyte having bicarbonate ions when dissolved in water and to increase the non-settling properties of the magnesium hydroxide particles when the mixture is added to water.

20. As a product, milk of magnesia containing less than 20% of dissolved and undissolved substances other than magnesium hydroxide, said milk of magnesia comprising a suspension of magnesium hydroxide particles in water and an electrolyte yielding bicarbonate ions in water solution, said electrolyte being eiiective to cause said milk of magnesia to be of a substantially more creamy and non-settling character than if said electrolyte were not present.

, 21. As a product, milk of magnesia of acreamy and very slight-settling character consisting essentially of magnesium hydroxide particles in suspension and an electrolyte consisting of carbonate of magnesium yielding bicarbonate ions in water solution which is effective in the amount present in said product to give the milk of magnesia substantially greater non-settling property than a milk of magnesia containing a similar proportion of magnesium hydroxide in substantially 4 pure water.

- and very slight-settling character consisting essentially of a suspension of magnesium hydroxide particles invthe neighborhood of 8% concentration and an electrolyte yielding bicarbonate ions 'in solution in effective amount to give the milk of magnesia such non-settling property that the milk of magnesia will not settle more than about 3% of its total volume in a period of 4 monthsj 24. A method of making milk of magnesia which comprises forming a suspension of magnesium hydroxide in water having less than 20% of dissolved and undissolved substances other than magnesium hydroxide and having incorporated therein an electrolyte yielding bicarbonate ions in water solution, said electrolyte being effective to give the milk of magnesia substantially greater non-settlingcharacteristics than a milk ofn agnesia similarly prepared but without the incorporation of said electrolyte.

25. A method of making milk of magnesia which comprises aerating a quantity of magnesium oxide power and adsorbing thereon by said aeration an amount of carbon dioxide that is adapted to form with water carbonic acid in effective amount to-increase the non-settling properties of a suspension of magnesium hydroxide made by treating the aforesaid quantity of magnesium oxide with water, and then making from said magnesium oxide a'water suspension of magnesium hydroxide stabilized by said carbonic acid. a v

26. A method of making milk oi magnesia which comprises calcining basic magnesium carbonate at a temperature of from about 900 F. to about 1800 F. to form magnesium oxide, forming a suspension or magnesium hydroxide particles in water by hydrating the resulting oxide in powdered condition with water until the bulk of the oxide has been converted to magnesium hydroxide, and then incorporating with the suspension an electrolyte yieldingbicarbonate ions in solution thereby substantially increasing the nonsettling property of the suspension of magnesium hydroxide particles beyond that possessed by it prior to the addition of said electrolyte.

27 A method of making milk 01 magnesia which comprises calcining basic magnesium carbonate at a temperature of from about 900 F. to about 1800? F. to form um oxide, adding an electrolyte yielding bicarbonate ions in means water solution to the resulting oxide, and form cles in water by hydrating said oxide in powdered condition with water in the presence of said electrolyte thereby producing a milk of magnesia having substantially greater non-settling property than a milk of magnesia similarly prepared but in the absence of said electrolyte.

28. A method of making milk of magnesia which comprises forming a suspension of magnesium hydroxide in water by hydrating maging a suspension of magnesium hydroxide partinesium oxide particles with water. said suspension including less than 20% of dissolved and lmdissolved substances other than magnesium hydroxide and having incorporated therein um carbonate eirective to give the milk of magnesia substantially greater non-settling characteristics than milk of magnesia similarly prepared but without the incorporation of said magnesium carbonate.

ROGER. A. msnmtm. 

